This invention relates to inductances fabricated on metal base printed circuit boards.
Various types of printed circuit boards are available for use as support bases for electrical components. Phenolic boards are in common use and are relatively inexpensive. Copper conductor lines are printed on these boards and connect discrete electrical components such as resistors, capacitors and inductors that are inserted into holes formed in the boards. Large area phenolic boards may require metal support frames to provide structural rigidity and prevent the boards from sagging and cracking under the weight of such relatively heavy components as transformers.
Metal base printed circuit boards provide relatively great structural strength. An insulating layer such as epoxy or porcelain enamel is deposited over the metal base and maintains electrical isolation between the metal base and the electrical components located on the board. The metal base also functions as a relatively good heat-sink to dissipate thermal energy developed by power devices located on the board.
On porcelain coated metal base printed circuit boards, it is possible not only to print metal conductors but also to integrally fabricate such electrical components as thick film resistors and delay lines. Relatively small valued inductors have been fabricated on such materials as fiberglass or solid alumina. It is desirable to also fabricate inductors and transformers on metal base printed circuit board. Such metal base printed circuit board inductances should be capable of fabrication with large inductance values and high-Q values, keeping resistive losses to a minimum.